It sounded, Kim Towery said, like "holy hell." Ms. Towery, a retired flight attendant, was inside her house on Charlton Heights Road in Moon on Saturday night when an enormous explosion leveled a home three doors down and seriously damaged at least three others. "A massive sonic boom," Ms. Towery said. "Everything shuddered and you heard flying glass." The blast, which firefighters said happened about 6:45 p.m. and could be heard miles away, injured two people, knocked in windows and sent debris flying, damaging as many as 14 other houses on the leafy suburban street of single-family homes, where pieces of insulation and shingles hung in trees like confetti Sunday. Shawn Landa, 47, who lived at 1656 Charlton Heights Road, which was totally destroyed in the explosion, was found underneath rubble in his front yard, neighbors and firefighters said. He was flown to UPMC Mercy with second-degree burns covering about 12 percent of his body and a broken rib, said Don Brucker, Allegheny County chief deputy fire marshal. A nursing supervisor at UPMC Mercy said Mr. Landa remained in intensive care Sunday evening. His condition was listed as serious.